OSPF Default Routing

OSPF Default Routing
Case 1 - Advertise  Route when default route in routing table

R6

router ospf 10
 network 6.6.6.6 0.0.0.0 area 3
 network 16.0.0.0 0.0.0.255 area 3
 default-information originate metric 60 metric-type 1

ip route 0.0.0.0 0.0.0.0 Null0

R1 

O*E1  0.0.0.0/0 [110/61] via 16.0.0.6, 00:00:10, FastEthernet0/0

Case 2 - Advertise  Route when default route not in routing table

now we will remove Default Route, So R6 will not have any default route in Routing Table.

Other area will  not have any default route.

R6

router ospf 10

default-information originate always metric 40

R1

O*E2  0.0.0.0/0 [110/40] via 16.0.0.6, 00:01:50, FastEthernet0/0

Case 3 -  Default route generate only when Loopback 1 66.6.6.6/32 is in routing table.

R6

R6#sh ip int br | in Loopback1

Loopback1                  66.6.6.6        YES NVRAM  up                    up

router ospf 10

default-information originate route-map loop1

//ip route 0.0.0.0 0.0.0.0 Null0 this  route is not required //

!

route-map loop1 permit 10

 match ip address 1

!

access-list 1 permit 66.6.6.6

R1

O*E2  0.0.0.0/0 [110/1] via 16.0.0.6, 00:00:01, FastEthernet0/0

Now in R6

int lo1

shut

%LINK-5-CHANGED: Interface Loopback1, changed state to administratively down

R1 

route will disappear as R6 does not have 66.6.6.6/32 in his routing table.

R1#sh ip route 0.0.0.0

% Network not in table

R1#

Case 4- Reliable Conditional Default Routing

track 1 ip sla 1 reachability

router ospf 10

 default-information originate always route-map track

ip route 106.106.106.106 255.255.255.255 Null0 track 1

ip sla 1

icmp-echo 9.9.9.9

ip sla schedule 1 life forever start-time now

route-map track permit 10

 match ip address prefix-list track

R1#sh ip route 0.0.0.0

Routing entry for 0.0.0.0/0, supernet

  Known via "ospf 10", distance 110, metric 1, candidate default path

  Tag 10, type extern 2, forward metric 1

  Last update from 16.0.0.6 on FastEthernet0/0, 00:01:49 ago

  Routing Descriptor Blocks:

  * 16.0.0.6, from 66.6.6.6, 00:01:49 ago, via FastEthernet0/0

      Route metric is 1, traffic share count is 1

      Route tag 10

R1#

R9

Now we will shut lo0  in R9

int lo0

shut

Loopback0                  9.9.9.9         YES NVRAM  administratively down down

R6

R6#sh track

Track 1

  IP SLA 1 reachability

  Reachability is Down

    3 changes, last change 00:00:33

  Latest operation return code: Timeout

  Tracked by:

    Static IP Routing 0

R1

Now we can see now in R1 no default route is from R6

R1#sh ip route 0.0.0.0

% Network not in table

R1#